This invention relates to the mixing of liquid and semi-liquid materials (hereinafter referred to collectively as xe2x80x9cliquidsxe2x80x9d).
Many liquids such as paints and varnishes require mixing prior to use, and ideally, many require periodic mixing throughout the period of use to prevent separation of the contents or to ensure that the surface layer does not become thick through evaporation. The most common method of mixing liquids in small containers such as paint tins is to stir them with a stick, but this is a very inefficient method of mixing and also presents a problem of disposal when the stick remains coated with the liquid.
When mixing liquids on a larger scale a common form of mixing device is a motorized impeller, but this is not very efficient for mixing viscous materials, and impellers are not easy to clean. Furthermore, the impeller and its associated drive system can impede access to the interior of the container, e.g. for inspection and cleaning purposes.
The present invention seeks to provide a new and inventive form of mixing apparatus.
The present invention proposes mixing apparatus which includes:
a liquid container having a bottom wall and a side wall; and
a mixing device having a generally planar mixing head disposed substantially parallel to said bottom wall, and a limb which extends substantially perpendicular from a peripheral edge region of the head adjacent to the side wall of the container for moving the mixing head up and down in said liquid.
Since the mixing head is normally disposed adjacent to the bottom wall of the container and the limb is disposed adjacent to the side wall the mixing device does not significantly impede access to the contents of the container. Thus, if the liquid is paint for example, after the initial mixing the device can remain in the container while the paint is removed, allowing the paint to be periodically agitated.
A preferred aspect of the invention is that the limb is provided with reciprocating means for moving the mixing head, the reciprocating means being located above the container and coupled to the limb by releasable connection means. In the case of a small container such as a paint tin the releasable connection is preferably located within the container so that the mixing device can remain within the container allowing the container to be resealed if desired. The mixing device can be manufactured relatively cheaply so that it can be disposed of with the container. In a simple form the reciprocating means may comprise a grasping handle for attachment to the limb externally of the container so that the handle may be grasped clear of the liquid without risk of major contamination with the liquid. The handle can be reused a number of times with the same or another mixing device.
The mixing head could be of various shapes and configurations depending on the nature of the liquid being mixed. The mixing head preferably contains at least one aperture and preferably covers between 30 and 60 percent of the area of the bottom wall of the container. As the mixing head approaches the bottom of the container a high laminar flow is created at the bottom of the container which has the effect of carrying any settled materials into the body of the liquid. When the mixing head is static a proportion of any settled materials will lie on top of the mixing head and be lifted with it, assisting the re-mixing.